FIG. 1 is an exploded perspective view showing a major portion of a microwave oven having a conventional heater assembly, and FIG. 2 is an exploded perspective view showing the heater assembly for the microwave oven shown in FIG. 1.
As shown in the figures, a cooking chamber 11 for cooking food is provided in a cavity assembly 10 of the microwave oven. An upper surface and a rear surface of the cavity assembly 10 are defined by an upper plate 13 and a rear plate 15, respectively.
A cooling fan assembly 17 is provided at a front end of a side of the upper plate 13. In addition, a variety of electric parts such as a magnetron 18 and a high voltage transformer 19 are installed at a rear end of the side of the upper plate 13 corresponding to the rear of the cooling fan assembly 17. The cooling fan assembly 17 generates airflow for cooling the magnetron 18 and the high voltage transformer 19.
In addition, a porous portion 13A is provided at the other side of the upper plate 13. The porous portion 13A is provided with a plurality of vents formed in the form of a generally rectangular shape. The porous portion 13A is a portion through which the heat from a ceramic heater 21 and a halogen heater 22, which will be described below, is transferred to the cooking chamber 11.
Meanwhile, a heater assembly 20 is installed at a portion of the upper plate 13 corresponding to the porous portion 13A. The heater assembly 20 generates heat used for heating food and transfers the heat to the cooking chamber 11. The heater assembly 20 is provided with the ceramic and halogen heaters 21 and 22.
The ceramic and halogen heaters 21 and 22 substantially generate heat used for heating food in the cooking chamber 11. The ceramic and halogen heaters 21 and 22 are formed to extend in their longitudinal directions, and heating wires (not shown) are installed therein to extend in the longitudinal directions, respectively.
In the meantime, both ends of each of the ceramic and halogen heaters 21 and 22 are provided with terminals connected to both ends of each heating wire. A lead wire W1 is connected to each of the terminals. In addition, the ends of the ceramic and halogen heaters 21 and 22 are provided with insulators 21A and 22A, respectively.
The ceramic and halogen heaters 21 and 22 are fixed to a heater supporter 23. Fixing brackets 23B are provided on both ends of an upper surface of the heater supporter 23 corresponding to the ends of the ceramic and halogen heaters 21 and 22. The fixing brackets 23H serve to fix the ceramic and halogen heaters 21 and 22. In addition, the heater supporter 23 is fixed to the upper plate 13, with the ceramic and halogen heaters 21 and 22 being fixed to the heater supporter 23.
Further, a reflection plate 24 is provided above the ceramic and halogen heaters 21 and 22. The reflection plate 24 serves to reflect the heat of the ceramic and halogen heaters 21 and 22 to the cooking chamber 11, i.e., downwardly. As specifically shown in FIG. 2, the reflection plate 24 is formed to have a cross-section of two successive trapezoids corresponding to the respective ceramic and halogen heaters 21 and 22. The reflection plate 24 is formed with a plurality of vent holes 24H. The vent holes 24H define passages for allowing air to flow for cooling the ceramic and halogen heaters 21 and 22.
Supports 24A and 24B are provided at both ends of the reflection plate 24 corresponding to the ceramic and halogen heaters 21 and 22, respectively. The supports 24A and 24B extend from both the ends of the reflection plate 24 to incline downward. In addition, the supports 24A and 24B support the ends of the ceramic and halogen heaters 21 and 22 fixed to the fixing brackets 23B of the heater supporter 23, respectively.
In addition, fixing flanges 25 are provided at both side ends of the reflection plate 24 perpendicular to the supports 24A and 24B. The fixing flanges 25, which are brought into close contact with the upper plate 13, are formed with a plurality of through-holes 25H for fixing the reflection plate 24.
A pair of heater covers 27 and 28 are provided above the reflection plate 24 in order. The heater covers 27 and 28 serve to prevent heat and microwave of the ceramic and halogen heaters 21 and 22 from being transferred out of the cooking chamber 11, i.e., in the microwave oven.
Reference numeral 13H, which has not yet been described, designates a fastening hole formed in the upper plate 13, and reference numerals 27H and 28H designate through-holes formed in the heater covers 27 and 28, respectively. The fastening holes 13H and through-holes 27H and 28H are portions which fastening screws S1 are fastened to or penetrate through, respectively, in order to fix the heater assembly 20 to the upper plate 13.
However, the conventional heater assembly for a microwave oven has the following problems.
Since the interior of the halogen heater 22 should be maintained in a vacuum state with halogen gas filled therein, the halogen heater 22 is installed to the heater supporter 23 with the insulators 22A previously fixed to the halogen heater 22. However, since the insulators 21A are fixed to the ceramic heater 21 during a process of manufacturing a microwave oven, the insulators 21A may incompletely insulate the ceramic heater 21 due to working errors and the like. Therefore, in the ceramic heater 21, the heating wire that expands by overheating is brought into contact with supports 24A of the reflection plate 24, thereby potentially causing sparks.
In order to prevent such a phenomenon, there may be provided a cooling fan for dissipating heat of the ceramic heater 21 in addition to the cooling fan 17 for cooling electric parts. Therefore, in such a case, there is a disadvantage in that the configuration of a microwave oven is complicated.